Open source tools in automation testing

Since this is my very first blog, I would like to discuss a very basic topic i.e. Use of open source tools in automation testing. There are a number of automation tools available in market for example selenium, watir, windmill, ranorex, soapUI, codeception etc. Among these tools which are open source such as selenium, soapUI and codeception have an edge over the ones which are not. Not only they are free to access but also you can find plenty of information about them online.
I had a chance to work with Codeception on a project and I must say it is one of the most user friendly and flexible tools around. It can be used to run test cases in local machine as well as on remote server like browser stack. As it follows behavior driven development approach, it works well with the requirements of the client. I am learning about more open source tools which can be used in automation testing to make the whole process cheaper, reliable and stable.